The absorbing measure of such device is given by so called expansion rate. The expansion rate is defined as a ratio of the chamber internal diameter to the internal diameter of an inlet duct and/or an outlet duct.
An exemplary embodiment of the absorbing device can be found in the U.S. Pat. No. 4,122,914, wherein an inlet tube leads into an internal space of an absorbing element, while a respective end of the inlet tube is tapered in the shape of an elongated nozzle and perforations are made before the tapered elongation. An outlet tube extends into the internal space of the absorbing element in such manner that parts of both tubes are parallel and are supported by partitions.
Another exemplary embodiment presents a construction design of an absorbing device described in the document JP 1986-184808 that presents a simpler construction solution, wherein both an inlet duct and an outlet duct lead into a chamber internal space, while an internal diameter of the inlet duct and the outlet duct in the absorbing chamber is first reduced and then enlarged.